For all due purpose, this is a duplicate of travel.stackexchange.com/questions/9245/… The exact situation is slightly different, but those differences are not relevant, and thus the answer is exactly the same.
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DocFeb 7 '13 at 18:50

1

However, questions should be closed if the questions are the same, not if it happens that the same answers apply.
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RoflcoptrException♦Feb 7 '13 at 19:24

As with all such questions: ask at a consulate or embassy!
That aside, ESTA is a tourist visa program, not a work permit. Therefore I'd expect it to not be valid for business travel (which yours would be). While they may not mind someone using it to attend a tradeshow for a few days, or a conference, as an agent for a foreign company, your plans are quite different. You're going to be putting a US resident out of a job (or preventing one from getting a job), which is the very reason foreigners need work permits as companies have to show they can't get local people qualified before a foreigner is allowed in to perform the work (or that's the theory at least behind such things).
But as said, ask at an embassy or consulate.

The Visa Waiver Program IS valid for business travel - it's definitely not a "tourist visa program"
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DocFeb 7 '13 at 7:59

but it's NOT a work permit, and for what he's doing he's going to require one!
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jwentingFeb 7 '13 at 8:00

@jwenting According to DHS the Visa Waver Program is valid for Business Travel as long as it is less then 90 days. And I am not sure what does any of this have to do with American resident being out of a job?
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KarlsonFeb 7 '13 at 17:14